A Piper Jaffray analyst now estimates Apple sold 600,000 to 700,000 iPads the first day.
Apple

If early sales estimates are any indicator, Apple appears to have another hit on its hands with the iPad.

Including presales, Apple sold 600,000 to 700,000 of the new tablet on Saturday, according to estimates released by Piper Jaffray senior analyst Gene Munster. That is more than double his earlier prediction of 200,000 to 300,000 first-day sales. At least 730 people lined up Saturday at Apple's flagship Fifth Avenue store in New York City--more than the number who showed up for the iPhone or iPhone 3GS launches, he said.

Munster's team polled 20 Apple stores around the nation on Saturday night and found that 19 still had tablets on hand. Twitter users reported mixed availability at Best Buy stores, the only retailer other than Apple that was supposed to have iPads in stock.

Apple could sell up to 7.1 million iPads worldwide this year, according to a preliminary forecast released Friday by iSuppli. Sales will double to 14.4 million units next year and triple to 20.1 million in 2012, the research firm predicts.